Process of closing collapsible tubes



April 1939- 0.1. was-rm 2,155,028

PROCESS OF CLOSING COLLAPSIBLE TUBES Filed Nov. 1. 1933 cans/v7 l4 mar/f5 M6242 Patented Apr. 18, 1939v rnocnss or CLOSING COLLAPSIBLE TUBES Charles J. Westin, Philadelphia, Pa., assignor to F. J. Stokes Machine Company, Philadelphia, Pa., a corporation of Pennsylvania Application November 1, 1933, Serial No. 696,145

3 Claims.

This invention relates to improvements in collapsible tubes and particularly to a new and useful improvement in collapsible-tube-closures, and methods of making the seal.

Collapsible or flexible tubes are used as dispensing containers for fluid or pasty materials such as toilet creams, medicinal ointments, foods, extracts, etc. The tubes are usually made of some suitable soft metal or alloy, but may also be made of a flexible or resilient material such as textile, paper, Celluloid, or other synthetic material. Each tube is comprised of a body portion with a relatively thin wall. One end of the tube is formed into a neck having a discharge opening and provision for receiving a cap. The other end of the tube is left open until the tube is filled and then closed by flattening the portion of the tube wall reserved and prepared for that purpose and sealing the closure by applying pressure or pressure and heat to cause the cement to set up or fuse and form a hermetic seam. To strengthen this closure, folds and tucks or bends may be. made in the flat or plain closure and the several members, each consisting of two thicknesses of tube wall and two or more coats of cement, thus forming a reinforced closure which is sealed by applying pressure or pressure and heat to'produce a reinforced hermetic seam.

Heretofore, it hasbeen the practice to make the closure by folding and bending the flattened, uncoated or untreated end of the tube several times and in many different ways and rely on the stiffness of the material in the folds to retain the relative close relationship or contact desired between the members of the closure, and to reinforce this closure and increase its burstingstrength an extra metal clip made from stiffer material has been used, or additional tucks or reverse bends have been resorted to.

Attempts to prevent leaking or increase the leak-resistance have been made by applying latex, waxes, or some anti-wetting compound to the inside of the tube wall at the point of closure and while this practice to some small extent increases the leak-resistance, it does not appear to be very, reliable. Tests indicate that this process, which may be called the caulking method, does not increase but rather lowers the burstingstrength of theclosure. v

I am also aware of the attempts made to produce astrong and perfectly tight closure bythe soldering method in which the tube is fluxed before filling in the hope of producing a soldered seam when the tube is closed. Methods have also been suggested of dipping the closure in molten solder, or molding a casing 'of solder around the folds, or dipping insome compound like varnish or lacquer in order to provide a tight seam, but such methods have not proved commercially practical.

The losses suffered by many packers on account of leaky tubes have become a serious problem. Certain products have a tendency to break down and the oils or soaps separating out will creep through the folds and smear up the outside, and where the soaps contain alkali the outside finish of the tube is destroyed by corrosion. Another difficulty with non-air-tight tubes is the breathing action which-takes place with certain materials in changing temperatures, and which causes the product in the tube to ferment or decay.

Through my invention, collapsible tubes or dispensing containers are produced which are airtight and, in addition, have a closure of greater bursting-strength than any of the present known types with which special reinforcing clips, extra folds, etc., are used. i

Some of the features of my invention are: Furnishing suitable adhesive compounds or cements; applying coats of cement at a definite point or points of the wall or walls of tubes; making a plain closure by flattening the walls of the tube against each other; sealing the plain closure by applying suitable pressure and/ or heat;

and/or crimping'or indenting-to knit the walls together, to give the closure .an artistic or finished appearance. I

' The process consists in applying a suitable cement in a uniform coatingas a band, bands or rings, of the desired width at the open end of the tube, allowing the coatingtodry, and, after filling the tube, closing it by flattening the tube so as to bring the walls into intimate contact at the point reserved for the closure, applying pressure and/or heat to set and/or fuse the cement within the closure to seal it, and crimping the closure to knit the walls together and ornament the closure. The application of pressure, heat and crimping may be performed with the same set of pressers atthe one and same time.

The cements now used to seal tubes, according to my invention, may be broadly grouped under two classificationsplastic and thermo-plastic. It is evident that the nature and consistency of the cement is of prime importance if the desired strength of bond is to be obtained, regardless of the usual rough handling of the tubes in the process of manufacture and packaging. A

large number of different adhesives and cements are available in the open market, but most of p these, such as glue, ordinary nitrocellulose cements, rubber cements, etc., dry by the evaporation of the water. or solvents, and for this type of cement means must be provided so that the moisture or solvent can escape, while through my process the tubes are precoated and most of the moisture or solvents are removed before closing, some moisture and solvent might remain if that type of cement is used. The tubes'to be sealed are usually made from some impervious material and the cement used should, therefore, contain preferably no moisture or solvent but rather be of the fusible type or contain only a very small amount of the solvent-just sufllcient to keep the cement plastic and subject to the cementing or sealing action when put under pressure.

Out of some thirty different kinds and makes of cement tested, only three or four of them have most of the properties required and from these the present tube-sealing cements have been developed to meet the exacting demands placed on a compound-for this purpose. These cements must be of such consistency that they can be handled by present available equipment. They should be, after sealing, moisture-proof, and unaffected or repellent to alkali and most solvents and oils. They should dry sumciently (most of the solvent evaporated) after thecoating is applied so that the tubes. can be handled without destroying or mar-ring the film orcausing accidental adhesions to any contacting surfaces. The film or pre-coat on coated tubes in storage must remain flexible and the cementing properties unchanged, so that, when the coated surfaces are brought into intimate contact and suitable pressure and/or heat is applied with clamping jaws or pressers, a firm, hard, cement seal is made, but only between the coated surfaces, the pressers remaining clean and unaffected even when contacting a coated surface. While pressers made from ordinary steels are quite satisfactory in working on these cements-I have found that pressers made from other materials, or certain alloys such as stainlesssteel, may be preferable.

In the group of "plastic cemen may be included cements or adhesives. having some orv all of the following properties:

Consistency (viscosity) suitable for handling with available equipment such as spray-guns; Will form a uniform, solid pre-coat;

Pre-coat quick-drying (may be tacky but not sticky);

Pre-coat remaining flexible;

Pre-coat retaining. adhesive properties -.for a reasonable length of time;

Ere-coat strongly bonded to the coated surface, will .not peel off; and

Will form an air-tight, impervious and strong bond between the members of the closure with the application of suitable pressure. A cement of this type is sold under the trade-name Stokes #29. Hermatite Sealing Compound". A cement of the plastic type may be composed as follows:

Under theme-plastic" may be included such cements which can be applied in a thin coating strongly bonded even to an impervious material;

dry rapidly and sufliciently hard to permit the handling of the coated surface; remain flexible -thermo-plastic,

and retain their cementing properties a reasonable length of time (several months); and, upon closing the tube, by bringing the coated surfaces together and momentarily applying'pressure and heat, the cement'will fuse and set up quickly. producing an air-tight, impervious and very strong bond between the members in the closure. A cement of this kind is sold under the tradename Stokes #24 Hermatite Sealing Both of these cements produce a clear, nearly colorless, film which may be tinted to harmonize with the printing or decoration of the tube walls.

From the table below may be seen the superior strengths of tubes closed by this new and novel process as compared with the various types of closures in present use. A large number of tubes for each group were tested, the tubes being closed according to commercial practice, and the average results for each type of closure are given. It may be noted that tubes sealed with "plastic cemen are not as strong as those sealed with the but they are considerably stronger, offer greater leak-resistance, and have greater. bursting-strength, than the ordinary tubes having the same type of closure, and are quite satisfactory for many products that do not require a closure equal in strength to that of the tube wall.

As far as I am aware, no standard was ever adopted for comparing the strength of this type of container and the strength of the closure in relation to other structural members of the container. It was a well known fact that all the standard types of closures were ridiculously weak and unreliableas compared with the strength, for example, of the side walls of the tubes. No

'one knew just what the strength was. I discovered that, by my new process of treating the tube,aclosure ofunusualstrengthwas produced, and I therefore developed methods and apparatus for making comparative tests to definitely determine the strength of the varlousclosures. In "this research I found it necessary to adopt two terms as standards for expressing the results obtainedin'thetests and for distinguishingbetween the point at which leaks occurred and that of complete failure of the containers. It is evidentthatminuteopeningsvaryinginsizeexist betweenv all ordinary surfaces regardless of the way they are entwined or clamped together, and airwlllflnditswaythroughtheopenings and passages, particularly where the contents of the.

containerhasatendencytocreatevaryinginternal pressures with varying atmospheric conditions. objectionable and detrimental breathing. Cer- Itisthisconditionthatcreatesthetainliquids also have the tendency to worm th i way through, perhaps influenced by capillary action.

The terms leak-resistance" and "burstingstrength were arbitrarily chosen as they seemed to give a natural expression to the results as recorded. Other terms may, of course, be used as, for example, ultimate tensile strength in place of bursting-strength. The term leakresistance, as used in this connection, is expressed in pounds pressure as indicated on a standard hydraulic or pneumatic pressure gauge. Readings are taken first at the instant a leak is discovered. The tests here recorded were made by connecting the test specimen to a specially developed testing apparatus which-was so arranged that the internal pressure exerted in the specimen could-be read on the gauge. In order to aid in observing when a specimen started to leak, it was submerged in a clear liquid, such as water, and compressed air gradually applied to the system. The moment sufiicient pressure is built up within the test specimen to force the air through any existing opening or to stress the parts so that an opening is created, air bubbles will start to escape through the water; As the bubbles are forming at the leaking point, they are clearly visible in the water and a reading of the pressure is taken, which reading is used to indicate the leak-resistance.

A leaking tube may ap'pear perfect except when subjected to-atestsimilar to the one described above, and may withstand many times the pres sure recorded for the leak before it opens wide enough to cause the pressure, as indicated on the gauge, to drop, regardless of the increased supply of compressed air. The reading taken at this point I have termed bursting-strength,

because usually when this pressure is reached the lot of tubes tested. Tubes made from tin. Practically all .of the tubes were film, 4% long and had a wall thickness of .006 inch.

T Type of Leak re- Bursting closure Coatmg sistance strength 1 2. Plain No 0 2 2 Latex 0 0 3 2 PlasticcemenL. 8 8 4 2... Therm0-plastic. l2 l2 5 3 p Plastic cement" 14 15% 6 3 Thermo-plastic 19% I have also found that this new type of closure permits the use of narrower folds, resulting in a saving. The extra clip, of course, is no longer of any use and this cost is eliminated. This saving means a very desirable economy to large users of tubes.

The novelty of using thermo-plastic cements andheat-sealing thestube closure was disclosed and claimed in my Patent No. 2,028,112, issued January 14, 1936. The present application discloses some further improvements not discovered at the time of filing the above application and, therefore, not disclosed and claimed therein. This application also discloses the strength obtained by the novel use of plastic cement in sealing tube closures.

I disclaim from the scope of this application all the subject-matter patented to me in U. S. Patent No. 2,028,112.

Mention is here made of my co-pending applications for Automatic coating machines, Serial No. 692,404, filed October 6, 1933; and for Tube sealing machines, Serial No. 678,186, filed June 29, 1933.

Any type or style of crimps or corrugations may be used but I prefer the kind shown and described in my Patent No. 1,989,031, issued January 22, 1935.

In the drawing:

Fig. 1 is a view in perspective of a tube before it is closed;

Fig. 2 is a view in perspective, and partly in section, of a tube having the plain type of closure;

Fig. 3 is the same view as in Fig. 2 but the closure is crimped;

Referring to the drawing: Fig. lrepresents a standard tube, which may be made of any of the materials referred to in the specification. It has the usual thin walled body I], which may be painted or lithographed and lacquered in the usual manner and practice of the trade. At one end, the body ll terminates into a breast I2, which has a neck with provision for discharging the contents, and means for receiving and holding a cap IS. The bottom or opposite end of the tube from neck or breast I2 is left open to permit the tube to be filled through this end with the material it is to contain. At this end I coat the inner wall of the tube body H with a layer of cement in the form of a band or ring 14, this band being only of a width required for producing a seal when the tube is closed. This band may, of course, be applied in a thin film on the inside.

The plain type of closure is represented in Fig. 2. Here the tube has been pre-coated on the inside only because a film of cement on' the outside would be of no benefit. The tube walls are fiattened against each other to close the tubes and pressure, or pressure and heat, is applied, depending on the type of cement used in sealing the closure. The cement is indicated at M between the fiat surfaces [6 of the tube closure. It may be noted from the table that a comparatively strong closure is produced with either plastic" or thermo-plastic cement, exceeding in leakresistance all of the present type of closures.

A plain tube closure, reinforced by crimping, is represented in Fig. 3. The cement filmmay be noted at M and the fiat surface H has been crimped with a row of staggered indentations l8 to reinforce the closure. The table indicates, and actual practice confirms, a marked increase in strength for tube closures that have been properly crimped.

I prefer to provide a tube having, beyond the point to which it is filled, an excess of length. Beyond the point to which the tube is filled, allowing for the necessary space required in the tapering of the sides towards each other, it is compressed or flattened together, as indicated in Fig. 2, to form a standing portion or flattened tube end, or two thicknesses of the tube wall flattened in two-ply relation against each other, and constituting the stock from which the seal is formed. I

The sequence followed according to my process of closing and sealing collapsible tubes consists in the precoating of the open end in a band of desired width inside the coating being applied to the suitable excess of length provided -for forming the several seal elements, and then allowed to dry or set so that the solvent is expelled. This takes anywhere from fifteen seconds to several days, depending on the kind of cement used. It should be pointed out here that the cement here referred to forms a firm and strong bond with the tube wall and will not peel 01f regardless of whether the tube is made from animpervious material such as tin, lead,

etc., or a fibrous one like paper.

By means of the suitable cement developed for the closing 01' collapsible tubes, I produce a tube closureand seal which is impervious to most liquids and solvents and produce a truly hermetically sealed tube closure. This permits the dispensing with the clip and extra type of fold.

By the term tube-sealing cement, as used in this specification and claims, is meant the cements hereinbeiore classified as plastic" and thermo-plastic.

The term cement is used without any limiting significance and is intended to include all compounds useful for sealing collapsible tubes by adhering closely or-bonding adhesively to the walls of the tubes and uniting orcoalescing to- 4 form an homogeneous, hermetic seal.

By the terms sealing and sealed closure" as used in this connection is meant a closure of superior tensile strength produced as a result of the huh and strong bond established between the walls of the tubes in the closure, as distinguished from a closure in which attempts have been made to stop the leaks by the caulking" method where latex, gelatin or waxes are used. It will be noticed from table on page 3 that untreated tubes having the plain closure,

as shown in Fig. 2, have absolutely no recordable strength even when coated with latex. Al-

though not included in the table, tests were made to determine the strength of tube closures bags or liners impregnated with was or parailln did not show any recordable strength either.

On the other hand, tests made on paper tubes treated with my cements and sealed according to my new processshowed an average strength of the closure greater than the strength oi the paper walls. I

Through my new process of treating the open end of the tubes, regardless of the material it is made from, subsequently filling through the ,open but treated end, closing and sealing according to the methods shown and disclosed, a tube representing a finished product of manufacture is produced which has a closure showing a leak-resistance" well above 5 pounds even when the simplest and most economical or plain type 01 closure, such as that shown in Fig. 2, is used.

I do not intend to be limited save as the scope of the prior art and of the attached claims may process consists oi the following steps, applying cement to a portion of the wall of an open end of a tube to form an annular band or layer of cement completely encircling the axis of said tube, flattening said portion so that the opposite walls are adjacent each other with a layer or film oi. cement between them and thus form a flattened standing part of said tube, causing said cement to become homogeneous, and forming crimps in the walls of said flattened part.

2. A process according to claim 1 in which said cement is of the plastic classification.

3. A process according to claim 1 in" which said cement is of the thermo-plastic classification. 4

CHARLES J. 

